1. Field of the Invention
The present invention relates to a drive sprocket wheel slide restricting structure for a bicycle transmission which includes a derailleur.
A bicycle transmission is provided with a drive sprocket wheel which is driven by a drive shaft. A driven sprocket wheel body includes a plurality of driven sprocket wheels and is drivably connected with the drive sprocket wheel by an endless chain. A derailleur is provided for changing over the winding of the endless chain among the plurality of driven sprocket wheels of the driven sprocket wheel body. The bicycle transmission includes a slide member which is movable in the axial direction of the drive shaft between the drive shaft and the drive sprocket wheel. At the time of changing over the winding of the chain, the drive sprocket wheel can be moved in the axial direction of the drive shaft. The present invention relates to the structure which restricts an excessive sliding of the drive sprocket wheel in such a device. The drive sprocket wheel slide restricting structure of transmission has such a constitution that is not found in the prior art. Hereinafter, as the background art, the prior art in a similar technical field is introduced.
2. Description of Background Art
In an exteriorly mounted multi-stage transmission, a guide pulley is supported on a derailleur arm and a tension pulley on a rear hub of a bicycle. When the tension pulley is pushed to a hub side by any external force, a situation may arise wherein the tension pulley enters a rotational locus of rear wheel spokes and bites the rear wheel spokes. An example is known wherein an excessive movement of the tension pulley is restricted. A guard ring is provided over the whole region of the moving area of the tension pulley. See JP-UM-A-60-143092.